The present invention relates to an information transmitting apparatus for transmitting control information to terminal processors which control and observe a plurality of loads and, more particularly, to an information transmitting apparatus which is suitable for use in information transmission in the compartment of a motor vehicle and the like.
As an information transmitting apparatus for motor vehicles, a fundamental system is disclosed in U.S. Pat. No. 3,648,057. An information transmitting system is also shown in SAE PAPER 810174. As shown in these literatures, the information transmission in the compartment of a motor vehicle will be increasingly needed in the future.
For example, a number of electrical power operated devices such as various lamps, motors, etc., and a number of various kinds of sensors and the like (hereinbelow, referred to as loads) are arranged in a motor vehicle, and the number of those devices increases more and more in association with the electronization of motor vehicles. Due to this, the wirings and connections for transmitting control signals to the electrical devices and signals from the sensors and the like are extremely complicated and the number of them is very large, causing a large problem. As a method of solving this, a transmitting method has been proposed whereby a number of signals are transmitted by a single signal line. According to such a method, since a transmission line is commonly used, if an abnormal state such as disconnection or the like occurs in the transmission line, the whole transmission system would have lost its function. In this case, there is a fear of malfunction of each device (load) to be controlled by the transmission system, so that this is very dangerous.
It is therefore desirable that the terminal processors in the transmission system of motor vehicles have a circuit for detecting the abnormality of the signal transmission lines and fail safe means for determining the operations of the loads into the safe states if necessary.
One transmission system having fail safe means is disclosed in Japanese Patent Kokai (Laid-Open) No. 105490/80. However, the fail safe system disclosed in this Gazette is not a system which can be integrated.